FR2653613A1 - METHOD AND DEVICE FOR STARTING A SYNCHRONOUS MONOPHASE ELECTRIC MOTOR - Google Patents

Abstract

The method ensures the starting of a single-phase synchronous electric motor in a preferred direction of rotation. The motor rotor is pre-positioned on a specific pitch by at least one isolated single-wave current pulse (I1, I2, I3) of predetermined sign; then, the motor is supplied with "full wave" alternating current with a first half-wave (A) of opposite sign to that of the rotor pre-positioning pulse. Use is preferably made of several successive pulses (I1, I2, I3), of energies decreasing in time (t), synchronized with the wave (V) of the alternating electric network for supplying the motor. Particular application: motors for household electrical appliance programmers.

Description

The present invention relates to the control of a

  single-phase synchronous electric motor, and more particularly it concerns

  first, a method and device for starting such a

  motor in a preferred direction of rotation.

  In order to impose on a single-phase synchronous electric motor a determined direction of rotation, and thus a preferential starting direction, it is necessary to use an electromagnetic or mechanical type device, the latter type involving the use of a device called "anti-return device". ". A mechanical non-return device such as a cam, used conventionally, has several disadvantages - additional cost related to the necessary mechanical parts or parts, especially the cam integrated in the rotor of the motor and a

stop.

  - Annoying noise, especially at the end of life, amplified by the structure

  of the apparatus on which the engine is mounted.

  - Mechanical endurance of the whole limited to that of

anti-return device.

  - Random startup time and too important in

certain cases.

  The present invention aims to eliminate all these drawbacks

  by providing a method and device for starting a

  single-phase synchronous electric motor in an imposed direction, which does not require

  It does not use any particular mechanical means, in particular avoiding noise and wear problems, while being particularly reliable and also providing a stable start-up time at an economical cost.

  For this purpose, the process according to the invention consists essentially of

  to pre-position the motor rotor on a specific step by

  at least one isolated single-phase current pulse of predetermined sign

  completed, and then after sufficient time for the mechanical stabilization of the rotor on said step to supply the motor with full AC power.

  wave "with a first alternation of sign contrary to that of the impulse

  pre-positioning of the rotor.

  Thus, the invention provides a starting method which is purely electrical in nature, and which can be easily driven

  by an electronic motor control circuit, using a techno-

  analog or digital logic, the implementation of the process can be syndroinized on the wave of the AC power grid

  the engine, particularly with regard to the pulse or impulses

  rotor positioning. The principle of the invention therefore consists in bringing and stopping the rotor in a specific angular position, unless it has already occupied this position previously, then in actually starting the engine from this position of the rotor and in conditions well

  determined, to impose a direction of rotation.

  In practice, however, the pre-positioning impulse of the rotor must satisfy certain conditions, with regard to its energy, and thus the average current of this pulse: Thus the energy of the prepositioning pulse must be at least equal to a lower limit value, which is necessary, under given power and ambient conditions, to overcome the resistant and inertial couples, and to take a step in the case

  o the rotor is not initially on the specific step in the contrary case

  re, the pulse simply confirms the rest position of the rotor.

  In addition, the energy of the pre-positioning pulse must not exceed an upper limit value, corresponding to the maximum accelerating torque beyond which the rotor would cross several steps

  and stabilize on a random position.

  The lower and upper limit values define,

  relative to the desired voltage intervals of the alternative power supply network

  temperature and ambient temperature, a control range to be

  ter to impose a start direction.

  In a preferred embodiment of the method according to the invention, to take into account all the dispersions, particularly related to the variations of the control parameters and the components, the rotor is pre-positioned on a specific pitch by several current pulses. successive monoalternances, isolated in time, all of the same sign but different energies from each other. For example, a succession of current pulses of decreasing energy in time is provided here, the first pulse being that of greater energy.

  and the last impulse being that of lower energy.

  The use of such a sequence of pulses ensures that at least one of the pulses belongs to the control range to be respected. This ensures, in combination with the degression of energies

  of the pulse sequence, that the last current pulse suffices

  In order to position the rotor in a correct pitch, it is not thwarted by the next pulse or pulses, which is necessarily too weak for the rotor to pass. The rotor remains on a position

  stable after the pulse train, regardless of the

previously mentioned.

  The invention also relates to a device for implementing the method defined above for starting an engine

  synchronous electric single phase in a preferred direction of rotation.

  This device essentially comprises, in combination, a bidirectional controlled switch connected in series with the motor, an electrical pulse generator whose output makes it conductive

  the controlled switch, and means for synchronizing the gen-

  pulse generator on the AC power supply

  of the engine, the generator being designed to control, using the

  switch, the power supply of the motor by at least one pulse of current monoalternance of predetermined sign, intended to pre-position the rotor, then the supply of this motor with AC "full

  wave ", with a first alternation of sign contrary to that of the impulse

pre-positioning.

  The bidirectional controlled switch in relation to the current pulse generator may be a triac, while the means for the synchronization of the electrical pulse generator on the AC network are advantageously constituted by a detector

  zero crossing of the AC voltage of this network.

  In the case of the generation of a succession of pulses of decreasing energies, the generator is provided to make the controlled switch with increasing delay times compared to times of zero crossing of the AC voltage of the network. , so as to obtain successive current pulses of energies

  decreasing in time. In other words, the energies of the sequence

  This pulses are "calibrated" by phase control.

  Anyway, the invention will be better understood using

  of the following description, with reference to the attached schematic drawing

  representative, by way of nonlimiting example, an embodiment of this device for starting a single-phase synchronous electric motor, and illustrating the operation of said device: Figure 1 is a block diagram of a device according to the present invention; Figure 2 is a diagram of electrical signals generated by

  or used by the device of Figure 1.

  In FIG. 1, reference numeral 1 denotes a single-phase synchronous electric motor, powered from an alternating voltage V,

  between two terminals 2 and 3, by a single-phase alternating network. An interrup-

  bidirectional controlled power unit 4, such as triac, is mounted

  in series with motor 1 between supply terminals 2 and 3.

  An electric pulse generator 5 has a

  output 6 connected to the control electrode of the switch 4, the pulses

  sions emitted by the generator 2 making the switch 4 conductive.

  The electric pulse generator 5 is itself synchronized to the AC supply network of the motor 1 by means of a zero detector 7, that is to say a device which detects the passages by a

  zero value of the AC voltage V of the supply network.

  The operation of the device, at the start of the engine 1, is explained more precisely by the diagram of FIG. 2, whose superposed lines respectively represent, as a function of time t: the AC voltage of the supply network V, between terminals 2 and 3; the signals Z delivered by the zero detector 7; the voltage Vm under which the motor I is actually powered at a given instant;

  the intensity Im of the current flowing through the motor 1.

  The signals Z, delivered by the zero detector 7 to the generator 5, are periodic pulses whose frequency is double

from that of the supply network.

  In the example considered here, the device is designed to send to the motor 1 three successive current pulses II, I2 and 13 of prepositioning of the rotor, all of positive sign, and of energies

decreasing.

  These pulses are obtained by rendering each time the triac 4 conductor after a certain delay time TI, T2 or T3 after a passage time t1, t2 or t3 of the voltage V by a zero value, with the voltage passing then from a negative value to a positive value, the delay time being controlled by the generator 5. The triac 4 then remains conductive until the next zero crossing of the voltage V. The first delay time T1, relatively small, leads to obtaining

  tion of a first current pulse II of relatively high energy.

  The second delay time T2, larger than the first, leads to obtaining a second current pulse I2 of lower energy. Finally, the third delay time T3, even bigger

  second, leads to a third pulse of

  B3 energy even lower.

  After the third current pulse 13, the device detects a new moment of passage t4 of the voltage V by a zero value, but with the voltage then passing from a positive value to a negative value. From this moment t4, the triac 4 is controlled so as to be permanently conducting. The electric motor is thus powered with alternating current "full wave", with a first alternation A of

  negative sign, which ensures the starting of the engine in a particular direction.

  mine. The invention is applicable, inter alia, to single-phase synchronous electric motors incorporated in the programmers of household electrical appliances, such as dishwashers and washing machines, these motors ensuring the rotational drive of a cam block which order

  itself a number of electrical switches. In this application

  cation, and more particularly if it is a "hybrid" type programmer, the engine is already controlled by an electronic circuit which controls in particular the duration of the program step; it is then easy to incorporate in this electronic circuit the functions of the device object of this

  invention, to impose the engine a direction of startup.

  It goes without saying that the invention is not limited to the only

  embodiment of this device for starting an electric motor.

  than single-phase synchronous which has been described above, as an example; it embraces, on the contrary, all variants of implementation and application respecting the same principle. Thus, one would not depart from the scope of the invention by changing the number of prepositioning pulses, or by reversing the sign of these pulses, provided that the supply is then carried out with a first alternation of

  opposite sign to that of the pre-positioning pulses.

Claims (10)

  1. A method for starting a single-phase synchronous electric motor, ensuring the starting of the motor in a preferred direction of rotation, characterized in that it consists in pre-positioning the rotor of the motor (1) on a specific pitch by means of minus one isolated mono-alternating current pulse (II, I2, 13), of predetermined sign, then after a sufficient time for the mechanical stabilization of the rotor on said pitch, to supply the motor (1) with "full wave" alternating current with a first alternation (A) of opposite sign to that of   the pre-positioning pulse of the rotor.   2. A method for starting a single phase synchronous electric motor according to claim 1, characterized in that the rotor is prepositioned on a specific pitch by a plurality of successive single-phase current pulses (II, I2, 13) isolated in time,   all of the same sign but different energies from each other.   3. A method for starting a single-phase synchronous electric motor according to claim 2, characterized in that   the rotor is pre-positioned on a specific step by a succession of pulses.   current flows (I1, I2, B3) of decreasing energies in time (t).   4. Method for starting an electric motor   single-phase synchronous system according to one of claims 1 to 3,   characterized in that the prepositioning pulse (s) (II, I2, B) of the rotor are synchronized to the wave (V) of the alternative electric network engine power supply (1).   5. Device for implementing the start-up method   a single-phase synchronous electric motor in a preferred direction of rotation according to claim 4, characterized in that it essentially comprises, in combination, a bidirectional controlled switch (4) connected in series with the motor (1), a generator (5) electrical pulses, the output (6) of which makes the controlled switch (4) conductive, and means (7) for the synchronization of the pulse generator on the AC electrical supply mains of the motor, the generator   (5) being provided for controlling, with the help of the switch (4), the power supply   of the motor (1) by at least one pulse of current mono, (I1, I2, B3) of predetermined sign, intended to pre-position the rotor, then the supply of this motor with alternating current "full wave", with a first alternation (A) of opposite sign to that of the impulse pre-positioning.   6. Device according to claim 5, characterized in that the bidirectional controlled switch, in connection with the generator   (5) electrical pulses, is a triac (4).   7. Device according to claim 5 or 6, characterized in that the means for the synchronization of the generator (5) of electrical pulses on the AC network consist of a detector (7)   zero crossing of the AC voltage (V) of this network.   8. Device according to claim 7, characterized in that   the generator (5) of electrical pulses is provided to make   driving the controlled switch (4) with increasing delay times (T1, T2, T3) with respect to times of zero crossing (tt, t2, t3) of the alternating voltage (V) of the network, so as to to obtain successive current pulses (I1, I2, B1) of decreasing energies in time (t).   9. Device according to any one of the claims   to 8, characterized by its application to a synchronous electric motor   single-phase (1) incorporated into an electronic device programmer menager.   10. Device according to claim 9, applied more particularly   the engine by a "hybrid" type   in that the functions of this device are incorporated in the electronic circuit which controls the motor and which controls in particular the duration of the program step.